This invention relates generally to determining the position of a moveable member, and more particularly to determining the linear position of a moveable member.
Determining a linear position of a moveable member has a variety of applications. For example, in order to know the position of a work tool of a work machine, such as a blade of a motor grader or a bucket of a wheel loader or excavator, the extension of a hydraulic cylinder that controls the position of the blade/bucket is often measured. These hydraulic cylinders are often quite long, ranging up to several meters in length.
In the past, conventional bar code type markings have been placed on the rods of hydraulic cylinders. By reading the bar code, the position of the rod within the cylinder may be determined.
One problem with this system is that complex markings are typically required in order to cover the significant length of the rod (in order to provide sufficient permutations of the code). These complex markings require relatively large amounts of processing power to decode. The processing power may be reduced by using a less complex code, but this typically results in a shorter length of the rod being marked by the code (because the code exhausts itself of combinations).
The present invention provides apparatus and methods for determining a linear position of a moveable member having a code disposed thereupon. The code includes a succession of data fields having at least n characters and including a frame-synch symbol at predetermined intervals in the code. A sensor reads the code on a predetermined portion of the moveable member. The predetermined portion of the member includes code having at least one frame-synch symbol and n characters. The sensor transmits a data signal as a function of the read code. A processing device is coupled with the sensor to receive the data signal. The processing device transmits a position signal as a function of the data signal, with the position signal being indicative of the linear position of the moveable member.